An alkylation process, which is disclosed in U.S. Pat. No. 7,432,408 (“the '408 publication”), involves contacting isoparaffins, preferably isopentane, with olefins, preferably ethylene, in the presence of an ionic liquid catalyst to produce gasoline blending components. The contents of the '408 patent are incorporated by reference herein in its entirety.
An ionic liquid catalyst distinguishes this novel alkylation process from conventional processes that convert light paraffins and light olefins to more lucrative products such as the alkylation of isoparaffins with olefins and the polymerization of olefins. For example, two of the more extensively used processes to alkylate isobutane with C3-C5 olefins to make gasoline cuts with high octane numbers use sulfuric acid (H2SO4) and hydrofluoric acid (HF) catalysts.
As a result of use, ionic liquid catalysts can become deactivated, i.e. lose activity, and may eventually need to be replaced. Alkylation processes utilizing an ionic liquid catalyst can form by-products known as conjunct polymers. These conjunct polymers generally deactivate the ionic liquid catalyst by forming complexes with the ionic liquid catalyst. Conjunct polymers are highly unsaturated molecules and can complex the Lewis acid portion of the ionic liquid catalyst via their double bonds. For example, as aluminum trichloride in aluminum trichloride-containing ionic liquid catalysts becomes complexed with conjunct polymers, the activity of these ionic liquid catalysts becomes impaired or at least compromised. Conjunct polymers may also become chlorinated and through their chloro groups may interact with aluminum trichloride in aluminum trichloride-containing catalysts and therefore reduce the overall activity of these catalysts or lessen their effectiveness as catalysts for their intended purpose.
Accordingly, there is a need for a method for determining ionic liquid catalyst deactivation so that deactivated ionic liquid catalysts can be effectively and efficiently replaced when appropriate.